a) Field of the Invention
The present invention relates to a driving circuit for a switched reluctance motor.
b) Description of the Related Art
Recently, a switched reluctance motor (hereinafter, often referred simply to as SRM) has been developed.
A rotor of the SRM is constituted by a lamination of silicon steel plates and its outer peripheral surface is formed with a plurality (for example, four) of salient poles.
On the other hand, a stator of the SRM is provided with a plurality (for example, six) of salient poles along its inner peripheral surface on which respective windings are wound is a lump manner. When the windings are sequentially energized, each salient pole of the stator on which the corresponding winding is wound attracts the adjacently facing one of the salient poles of the rotor to develop a torque on the rotor.
FIG. 1 shows a general concept of the SRM.
In FIG. 1, the rotor 1 to be revolved in the direction of n is provided with four salient poles 1a, 1b, 1c, and 1d on its peripheral surface. It is noted that three windings 2a, 2b, and 2c are wound on the salient poles (not shown) of the rotor of the SRM.
A current caused to flow through each phase of the windings 2a, 2b, and 2c is switched by means of switching devices so that developed magnetic fluxes thereon are moved sequentially in a rotation direction of the rotor, thus the rotor 1 being revolved.
FIG. 2 shows a graph indicating a variation in a whole inductance La of the one winding 2a of the stator of the SRM shown in FIG. 1 with respect to a revolution angle .theta. of the rotor 1. It is noted that when the winding 2a on one of the salient poles of the stator has just faced against the two symmetrically arranged salient poles 1a and 1c, the revolution angle .theta. indicates zero.
An industry demands a drive circuit for the SRM which can improve a circuit efficiency, can solve a problem of electromagnetic wave interference, and can increase more an output torque of the SRM.